Just to add with what you said (and I agree with), Fame:
There was another, alternative version to Fabrizio's death that was actually filmed but never released in any version, theatrical or "Saga." Harlan Lebo, in the excellent, "The Godfather Legacy," reproduces a couple of stills in which Michael (dressed in patented gangster mufti--pearl gray fedora and black overcoat) personally kills Fabrizio in his pizza parlor. I'm guessing that this version was never used because it would have been totally illogical (to say nothing of risky) for Michael, already the Boss of Bosses, to personally commit a murder, even if it was to avenge his wife, when he had lots of qualified gunmen to do the job for him. But, what I would give to see that scene!

The Saga version is far and away the best version, for the reasons Fame said.